oeqa/sdkext/devtool: Ensure dependencies for test_extend_autotools_recipe_creation are present

test_extend_autotools_recipe_creation needs libxml2 so ensure this is
installed/present as it may not be in the minimal eSDK case.

(From OE-Core rev: fb274c7fe588c556936a0df1ae583907875c2a76)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/sdkext/cases/devtool.py

@@ -68,6 +68,7 @@ class DevtoolTest(OESDKExtTestCase):
     def test_extend_autotools_recipe_creation(self):
         req = 'https://github.com/rdfa/librdfa'
         recipe = "librdfa"
+        self._run('devtool sdk-install libxml2')
         self._run('devtool add %s %s' % (recipe, req) )
         try:
             self._run('devtool build %s' % recipe)